Summary An Air Canada Airbus A330-300 (registration C-GHKX, serial number0412), operating as FlightACA216, departed Vancouver International Airport, British Columbia, at 1423 Pacific standard time on a scheduled flight to Calgary, Alberta, with 6crew members and 92passengers on board. Shortly after take-off, the Vancouver tower informed the pilots that a substantial amount of smoke or vapour was coming from the number2engine. Although the pilots did not receive any abnormal engine indications or cockpit warnings, they declared an emergency and advised that they were returning to Vancouver. After an uneventful landing, the pilots shut down the number2engine. Aircraft rescue and firefighting services, following the aircraft, advised the pilots that fuel was leaking from the engine but there was no sign of fire. Eventually, the aircraft was towed back to the terminal where the passengers were deplaned. There were no injuries or damage to the aircraft. Ce rapport est galement disponible en franais. Other Factual Information During a routine service check of C-GHKX the day before the occurrence, maintenance personnel found fuel leaking from the drain mast on the number2engine (Rolls-Royce RB211 TRENT772B-60/16, serial number41102). Further investigation showed that fuel was leaking from the air/oil heat exchanger. On the AirbusA330, engine oil is cooled by the air/oil heat exchanger. A torque motor automatically directs high-pressure fuel through a jet pipe to a piston that opens or closes an air valve to control oil temperature. The fuel leak exceeded the limits prescribed in the AirbusA330 troubleshooting manual (TSM). Maintenance entered the defect, including the corrective action required, into the aircraft maintenance logbook and removed the aircraft from service at approximately 1300 Pacific standard time.1 The aircraft was then towed to an Air Canada hangar to replace the air/oil heat exchanger. A notation was made, by mistake, on the maintenance office duty board, indicating that the aircraft required a fuel/oil heat exchanger replacement instead of the air/oil heat exchanger, as had been written in the aircraft logbook. Subsequently, a maintenance team of three licenced aircraft technicians, starting work at 2030, was assigned the task of replacing the fuel/oil heat exchanger. Figure1. Fuel/oil heat exchanger The technicians reviewed the air/oil heat exchanger defect in the logbook, noted the discrepancy with the duty board, and decided to check the fuel/oil heat exchanger first. It was decided that two of the technicians, one of whom was authorized by Air Canada with maintenance release authority for the AirbusA330 and the TRENT 700engine, would troubleshoot the suspected leak. They disconnected a low-pressure (LP) inlet coupling to the fuel/oil heat exchanger (seeFigure1), and fuel sprayed from the disconnected line. Confirming that the fuel/oil heat exchanger was not the source of the leak, the technicians prepared to reconnect the LP fuel line and ordered replacement seal rings. Some time later, the inlet coupling was reattached to the fuel/oil heat exchanger and the three bolts were tightened to the correct torque. However, a retainer, a crucial component to the security of the coupling, was omitted. The technicians who removed the LP fuel line on the fuel/oil heat exchanger were unfamiliar with the style of coupling used and did not refer to the AirbusA330 TSM, nor did they refer to all relevant sections and pages of the aircraft maintenance manual (AMM) when removing or reinstalling the LP fuel line. In addition, the removal and reinstallation of the LP fuel line was not recorded on any maintenance documents, contrary to Air Canada's maintenance policy manual and Transport Canada regulations. Once the LP fuel line was reinstalled, the connection was inspected for leaks and security from an elevated platform in the hangar. The two technicians resumed troubleshooting the fuel leak, this time using the Airbus A330 TSM, and determined that the source was the air/oil heat exchanger, as identified in the aircraft logbook. It was also noted during this troubleshooting sequence that the LP connection on the fuel/oil heat exchanger was not leaking fuel. They removed and replaced the defective air/oil heat exchanger. Referencing the A330AMM, the technicians ran the engine at idle for six minutes. Once the engine run was complete, the connections were inspected for leaks from the ground. The air/oil heat exchanger may be inspected from the ground, but an inspection of the LP fuel-line connection on the fuel/oil heat exchanger requires the use of an elevated platform, as required by the A330AMM. The A330AMM also requires the use of a special developer on the reassembled components that aides in detecting fuel leaks. Neither an elevated platform nor a developer was used for the inspection of the fuel fittings and detection of leaks. No discrepancies with the LP fuel line connection or leaks were noted. All appropriate paperwork for the replacement of the air/oil heat exchanger and the subsequent engine runs was completed, and the aircraft was returned to service. The following day, the aircraft departed for Calgary, Alberta, as FlightACA216. The taxi and the take-off roll were normal. The departure was during daylight hours and in clear weather conditions, and pilots of another aircraft waiting to depart observed a fuel leak from ACA216 as a significant vapour trail (see Appendix A). The pilots of that departing aircraft informed the Vancouver tower of the vapour trail coming from the number2engine of ACA216, and, in turn, the Vancouver tower relayed this information to ACA216. During the flight, the pilots received no abnormal engine performance indications or warnings from the electronic centralized aircraft monitoring (ECAM) system. The ECAM displays basic fuel data on the cruise page and will display detailed fuel information on demand. Later, the pilots determined that 3700kg of fuel was used above the normal consumption rate. There was no sign of a fuel spill on the apron or on the taxiway leading to Runway26L. However, a substantial amount of fuel was found at the threshold of Runway26L, where ACA216 departed. Transportation Safety Board of Canada (TSB) investigators and Air Canada maintenance personnel examined the engine and found that the LP inlet fuel line to the fuel/oil heat exchanger of the number 2 engine had detached. Although the fuel-line coupling appeared to be intact and the three bolts holding the coupling together were tight, the retainer was missing. The missing retainer was found further down the detached fuel line, obscured from view. The engine manufacturer, Rolls-Royce, indicated that it is possible, within the tolerance range of all the LP components, that the three bolts that hold the LP connection in place may not bottom out if the retainer is omitted. It is, therefore, possible to achieve torque of the proper value. In light of this scenario, the compression on the seal rings is possibly sufficient to prevent leakage at idle power. The flight data recorder (FDR) was removed from the aircraft and sent to Air Canada's maintenance facility in Dorval, Quebec, for downloading. The downloaded information was analysed by the TSB Engineering Laboratory. Rolls-Royce indicates that pressure in the LP fuel line increases from 100pounds per square inch (psi) at idle to approximately 190 psi at take-off power while the fuel flow rate increases from 685kg per hour to 9000kg per hour. Data from the FDR indicate that a fuel discrepancy began when engine power was increased for take-off. At take-off power, the fuel loss was calculated to be approximately 10000kg per hour, yet the engine continued to operate normally. The TSB determined that incidents of engine fluid loss following maintenance activities have occurred in the past. Between 1999 and 2000, there were three incidents in three different aircraft where the incorrect assembly of fluid fittings was not discovered during the required engine idle runs. Information from one engine manufacturer indicates that idle power ground runs can only be expected to detect 80percent of all engine fluid leaks. A test flight or a ground run at higher power settings, to create conditions such as increased fuel/oil pressures and sustained vibration, would be required to detect the remaining 20percent of leaks. At least one airline company in Canada requires a high-power engine run as standard practice after a component replacement that could result in fluid leaks. This airline, however, operates aircraft with different engines than those on the occurrence aircraft. Also, the engine manufacturer does not require a high-power run-up after engine maintenance. In August 2001, another Canadian-registered Airbus A330 made an emergency landing with both engines inoperative due to fuel exhaustion resulting from a severe fuel leak. As a result of the 2001 occurrence and a similar fuel leak in1997 involving an AirbusA320, Airbus Industrie issued Service Bulletin (SB) A330-28-3080. This SB provides AirbusA330 operators with instructions on how to activate fuel-leak monitoring software. Once activated, this fuel-leak monitor will alert the flight crew to a discrepancy of more than 3500kg between the initial fuel on board (FOB) and the total of the present FOB plus the fuel used (FU). When a discrepancy is detected, a single chime sounds and a FU/FOB warning is shown on the ECAM display. Compliance with this SB is recommended by Airbus but is not required by regulation. At the time of the occurrence, Air Canada had not implemented the SB on any of its AirbusA330 aircraft (seeSafetyActionTaken).